This ends the description of the Virtual Personal Assistant System. The system can function like every other calender application, but it brings the feature to plan events between other people, a feature that any calender on the market still misses. The difficulty of specifying a system that needs a lot of information from different sources is a tough job to do. 
The PA system described in this document does not exist and it could very well be that we did not take every aspect of such a system in consideration. In order to fully understand what is needed for such a system can only be achieved by actually building it.